Insect repellents



Patented Feb. 3, 1953 UNITED STATES i ATENT OFFICE INSECT REPELLENTS the Army No Drawing.

Original application January 10,

1949, Serial No. 70,142. Divided and this application October 4, 1951, Serial No. 254,631

1 Claim.

This invention relates to insect repellents. We have discovered that the application of an N-alhyl-suhstituted acyl anilide of the general formula wherein Y is an aliphatic acyl group, Z is hydrogen or a methyl group, and R is a straight chain alkyl radical, effectively repels insects, particularly the dedes aegypti and anopheles quadrimcculatus, when such compound is applied to the human skin or a fabric.

Tests to measure the repellency of the abovementioned compounds against insects by skin application were conducted by smearing the compound on the arms of test personnel, who then thrust their arms into cages containing insects. The arms were exposed for 30-minute intervals at 3 minutes each until the first insect bite.

Tests to measure the repellency of fabrics impregnated with the above-mentioned compounds against insects were conducted by uniformly impregnating mercerized cotton hose with the compound at a rate equivalent to 3.3 gms. per sq. ft, drawing the dried hose over the arms of test personnel, who then thrust their covered arms into cages containing insects for 1 to 2 minutes.

Examples of aliphatic acyl substituents whose attachment to the N atom of the anilide or toluidide (methyl ring-substituted anilide) confers insect-repellent properties, are formyl, acetyl and its higher homologues such as propionyl and butyryl and unsaturated acyl such as crotonyl groups; and examples of straight chain alkyl substituents for the remaining non-phenyl-suhstituted valence of the N atom of the anilide are the methyl, ethyl, propyl, n-propyl, and n-amyl groups.

We have found that the N-alkyl-eubstituted aoyl anilides contemplated by our invention are freely soluble in liquid dialkyl phthalates, e. g. in dimethyl phthalate (a Well known insect repellent) and that such solutions, e. g. solutions of the order of 20% or 50%, are more potent in e t repellents than the dialkyl phthalate alone; Solutions of these 'anilides in an aliphatic dihydric alcohol, e. g. in Z-ethyl hexanediol-LB, a well known insect repellent sold under the name 2 of Rutgers 612, also have excellent insect repellent properties.

The following table illustrates the results obtained by the above test methods against aedes aegypti and anopheles quadrimaculatus, as ex amples of insects against which the invention is applicable, by using compounds in accordance with the present invention:

Rcpellency on application to skin Repellcncy of Impregnatod A h 1 Fabric Aedes n01) as against 1 A (mm/pt, 'gm Acles atgz ptz Minutes Minutes N-n-butyl iormanilide 236 42 over days.

Do. Do. over days. N-ethyl acetamlide s01. 306 159 in dimethyl phthalate). N-ethyl acetanilide (50% sol. 328 108 in 2-ethy1 hexanediol-1,3). N-propyl-acetanilide over 36 days. N-n-propyl acetanilide (50% 308 237 sol. in dimethyl phthalate). N-n-propyl acctanilide (50% 377 128 sol. in 2-ethyl hexanedim-1,3). N-n-amyl acetanilido. 360 over 10 days. N-methyl propionanilid Do. N-n-propyl propionanilide 287 43 Do. N-n-butyl propionanilide 303 55 Do. N-namyl propionanilide 255 50 Do. N-znethyl butyranilide. l. 227 77 Do. N'methyl crotonanilide" 260 42 Do. N-cthyl crotonanilicle l. D0. N-methyl mctc-acetotoluidide. Do.

No'rn. Not determined.

It will be seen from the foregoing table that, generally speaking, the N-alkyl-substituted acyl anilides having two or more carbon atoms: in the acyl group (N-alkyl-substituted acetanilide and its higher homologues), possess insect repellent properties superior to those of the N-alkyl-substituted formanilides.

The insect repellency of the foregoing compounds and solutions compares favorably with and in many instances is superior to the insect repellency of dimethyl phthalate, as is shown by paired tests, wherein the tester smeared one arm with the anilide and another arm with dimethyl phthalate and simultaneously exposed both arms to cage insects; a test method more fully described in Chemical Abstracts, vol. 39, p.

3385. The following values were noted (repellency figures in minues; upper figure relates to anilide, lower figure to dimethyl phthalate) Rcpellency g ggg f gf 9n apphc? tion to skin,

tion to skm, Anopheles ae z quadrigyp maculatus N-n-butyl formanilide N-ethyl acetanilide (50% sol. in di- 306 159 methyl phtha-late) 254 136 N'n-propyl acetanilide (50% sol. 1n d1- 308 237 methyl phthalate) 282 192 N-n-amyl acetanilide N-n-propionanilide 3% N-methyl butyranilide N-methyl crotonanilide For ease of application the N-alkyl-substituted acyl anilides contemplated by the present invention may be incorporated in a suitable inert liquid or solid carrier, such as mineral oil, alcohol, petrolatum, etc. For facile and uniform fabric impregnation, they may be applied in an inert solvent, such as alcohol, ether, etc.

This application is a division of our copending application Ser. No. 70,142, filed January 10, 1949 (now abandoned).

Having thus fully described our invention, we claim:

An aecles aegyptz' repellent composition for application to the skin, comprising N-n-amyl acetanilide and a non-toxic insect-repellentadjuvant as -a carrier therefor.

PAUL D. BARTLETT. I-IYP J. DAUBEN, JR. ABRAHAM SCHNEIDER.

REFERENCES CITED The following references are of record in the file of this patent:

OSRD Insect Control Committee Report Number 28, Interim Report Number 0-94, May 18, 1945, publication date August 1, 1947, 50 pages, pages 1 to 4, 9, 14, 37 considered especially pertinent.

Linduska et al., Flea Repellents for Use on Clothing, J. Economic Entomology, December 1946, pages 767 to 769. V 

